Electronic devices such as liquid crystal display devices and semiconductor devices are generally manufactured by forming numerous layers of patterns on a substrate. A photolithography process has been primarily used so far in order to form such patterns. However, a photolithography process has problems in that a prescribed pattern mask needs to be prepared, the manufacturing process is complicated since chemical etching and stripping processes need to be repeated, and chemical wastes harmful to the environment are produced in large quantities. This soon connects to a manufacturing cost increase and lowers product competitiveness. A roll printing method using a printing roll has been proposed as a new pattern-forming method in order to solve such disadvantages of a photolithography process.
The roll printing method includes various methods, but is largely divided into 2 methods of a gravure printing method and a reverse offset printing method.
A gravure printing method is a printing method of coating an ink on a copperplate, scraping the excess ink and then printing, and is known to be suitable for printing in various fields such as for publishing, for packaging, for cellophane, for vinyl and for polyethylene, and researches for applying the gravure printing method in preparing an active device or a circuit pattern used in display devices have been made. The gravure printing method transfers an ink on a substrate using a transfer roll, therefore, a pattern may be formed with one transfer even for a large area display device by using a transfer roll corresponding to a target area of the display device. Such a gravure printing method not only forms an ink pattern for a resist on a substrate, but also is used in patterning various patterns of a display device, in the case of a liquid crystal display device for example, patterning metal patterns for a TFT, and for a gate line and a data line, pixel electrode, a capacitor connected to the TFT as well.
However, a blanket commonly used in a gravure printing method is prepared by casting a silicone-based resin in a hard master mold, and the blanket prepared as above has a limit in being prepared to have a uniform thickness, and also has a difficulty in mass production on a pilot scale. Accordingly, a reverse offset printing method is normally employed for forming an accurate micro pattern.
A reverse offset printing method is a very popular technology in terms that costs are saved and a production rate is improved in forming a pattern, however, a high-quality blanket is required in order to obtain an accurate pattern. Moreover, a cushion layer included in a blanket has an advantage in widening a printing pressure margin, but has a problem in that a thickness variation of the blanket becomes large since a thickness variation of the cushion layer becomes large due to nonuniform foam particle sizes.